Migration towards TOML configuration files

[deusebio]

TOML project config files are becoming a standard in python, introduced in PEP. Beside, some of the components that are used in the template (e.g. Black) can be configured only using TOML, and not via setup.cfg.

However, at the present point there is still some resistance for TOML to be fully integrated in Python, see for instance the discussion in flake8

There are few possibilities here:

1. Wait for TOML file to be a standard widely used and then migrate configuration from CFG to TOML. Meanwhile use both TOML and CFG files, depending on the tool to be configured
2. Stick to either TOML or CFG and rely on some workaround (e.g. minor packages) to integrate the configuration (e.g. this repo and references therein configures black with cfg, and this repo configure flake8 with TOML)
3. Migrate linting from flake8 to pylint (and stick to technologies that can be configured with TOML)

[NicolaDonelli]

No strong opinions about this: I don't know enough about configuration file formats to have one!

To me, as long as all our dependencies support the chosen config format (which does not seem the case for flake8 with toml), every format is fine.

Maybe it could be useful for the discussion if you could list here the main advantages of one against the other...

[deusebio]

TOML is a bit more advanced than INI/CFG, and it extends a bit the INI functionalities, e.g. allowing to have deeper nested structures. But it is really not much about the features of the configuration system on its own, but rather where python and its tools are going

It seems that the community eventually will get there, replacing setup.py and setup.cfg with TOML project files. However we are not there yet.

To be fair - right now there is no format that covers all the tools we use by default: flake8 does not support TOML and black does not support INI/CFG. However, I believe that one would generally want to configure linting rather than formatting. Linting usually has many configurable parameters (given the high level of customization that one wants for disabling only certain codes over others), formatting probably a bit less...

Anyhow, I guess we should choose one of the three options (or any other option you might have is of course welcome) listed above.

Of the three solutions, I honestly don't mind too much 1 and keep both file format (it is really just one more file, can't be that bad...). But given the momentum that TOML is getting, we could start migrating configuration files towards it for all the tools that support it (mypy, black, etc).